Machine Operation & Maintenance

[dapaq2]

Hello Group,

I am with a non profit all volunteer railroad museum. We have an ex military railroad locomotive that is equipped with a Caterpillar 3508 Engine in it and is giving us trouble by shutting down on its own and acts up depending on the temperature of the cooling water. The engine model number we have is a 3508 DI (letter i, not number 1). The serial number of the engine is 68Z00777. My understanding is that our 3508 engine was built in 1991. I dont know if this helps but the air filters are Square and not round, I see alot of photos of the 3508's with round filters, i think the round filters are on newer production/version of this engine. I think we have an older version. Also the arrangement number is LW4210.

Here is what we are experiencing.

For those of you who are not familiar with railroad locomotives. On a railroad locomotive we have numbered throttle positions from Idle, then 1 through 8 with number 8 being full or max throttle to control the engines RPM's. The oil and fuel pressures are running normal of at least 60 psi and above. When the cooling water temperature is anywhere from cold up to just short of 160 degrees the engine operates just fine and can rev the engine all the way up to full throttle (1250 RPM's as shown by the tachometer on the side of the engine) But as soon as the water temperature reaches 160 to 165 degrees, if I advance the throttle from number 4 (about 750 RPM's) to number 5 (about 925 RPM's), as soon as the RPM's start to increase from number 4 throttle to half way between number 4 and number 5 (approx 900 to 925) the engine shuts down just like you had pressed the Stop button. As we use the engine more and more the shut down issue becomes worse. The duration time between starting it back up and the time it takes for it to shut down becomes less. We have had it where the water temp would only be at about 170 to 175 degrees and the engine will shut down advancing the throttle to number 2 (about 450 to 500 RPM) and we restart the engine right away and within 5 to 8 seconds the engine shuts back down just while idleing. We can keep restarting it and it would shut down on us again within 5 to 8 seconds. We think it may have something to do with the "Engine Control Group" device or possibly the "Thermistatic Pilot Valve", or the "Water Temperature Contactor", or "Thermostats in the Manifold", or maybe even the Govener, but we are only guessing as to the culprit at this point and really need a professional to help us with this.

We are a very small non profit volunteer museum with very little money to work with. We would call one of the local cat dealer mechanic/technicians to come out to look at it but we dont have the money to cover their labor rate of $119 an hour. Is there anyone here that knows what is causing this shut down issue and can help provide information on what the cause is and what is needed to resolve the issue? Has anyone ever experienced a Cat 3508 with this kind of behavior and was able to fix it? We would be grateful to anyone who can help us.

Thank you kindly,

Doug

[mikel]

One of the first things I'd suggest is validating the water temperature sensor signal, the low cost way it a small portable heat bath, I used to use a small Fry Baby deep fryer, filled with mineral oil and a good reliable thermometer. Take the sensor out of the engine, put in in the bath, slowly increase the temperature in 20 degree increments, and see where you get the fault. Does your control system show a display for the temperature or does it just trip when it reaches the threshold? The temperature sensor is the mostly likely culprit, also check the gauge you use to monitor, in may cases they can also be defective and may be reading low.

Your description sounds like a real temperature related problem.

Most dealerships are run and staffed by pretty civic minded people, have you tried asking the Service Manager if he would help you out?  Or go up the food chain a bit and see if the Division Manager or the head guy will help you out with a little labor support?  Worst case is that you'll get a NO answer, but you also could get a yes and maybe get a dealer mechanic or two interested in helping you out on a volunteer basis.

Try providing some details about where your from, someone from the forum may be able to steer you some better help.

Hope that helps, Mike L.

[dapaq2]

Hello Mike and thank you for your reply,

The water temperature gauge that we are getting our temperature readings from is located on the Locomotives control stand and uses a capillary tube that runs from the gauge to the engine manifold. We tested its reading against one of those infrared temp guns and the temperature gauge showed to be off by only about 1 degree, so we are considering the water temperature gauge that we have been reading from as accurate. There are no other temperature displays or gauges anywhere else on the locomotive. When the gauge on the control stand shows the temp at exactly 160 degrees or higher, the engine starts shutting down like described in my original post.

But based on what your telling me, Is it safe to assume that possibly and most likely the cause is the "Water Temperature Contactor"?, which I beleive is located up near the area of the Themostat Manifold? My understanding is that that sensor is non adjustable and do go bad from time to time. Would the thermostats located up in the thermostat manifold if stuck partially closed restricting water flow to the radiators be a possible cause, or would this shut down issue be caused strictly by the water temperature contactor or other similar temperature sensor being out of adjustment or just plain defective? As far as removing the water temperature contactor and testing it first, If you think that device might be our best bet as to being the source of the problem, if these are not expensive units maybe we would best to go and see if we can afford to buy a new one and swap them out vs testing it first to save us some time? We dont have a deep fryer to test it, and if there is a very good chance that it could be the for sure possible cause, it might save us the time vs trying to verify it accuracy first. My understanding is that we have to drain the cooling water below the thermostat manifold before we can gain access to this area because our radiators are mounted higher (locomotive) than the top of the engine manifold and if we have to go through all that first just to verify its accuracy we may as well replace it with a new one. After all its over 20 years old. 1991 Thoughts?

If you guys are curious, I am with the Michigan Transit Museum, Mount Clemens, Michigan. www.michigantransitmuseum.org At this point we can use all the help we can get. We have already spoke with Michigan Cat in Novi Michigan, they are unwilling to help us at any cost to them. We even asked if they would donate a pair of new air filters at a cost of about $126 each, the answer was NO. We own two locomotives, but the other one needs new batteries and a water pump and wont be able to get it up and running anytime soon, and this engine with the shut down issue is our only "Usable" engine, and if we cant get it going very soon we are going to be forced to shut down our operations by next spring due to running out of money. Our locomotive allows us to provide train rides to the public and the train ride fares are what keep our museum operating. Without an operating locomotive we cannot provide train rides. And without incoming fare money, donations, and volunteers we would not be able to exist.

If anyone can help us please do let me know. I am available by telephone if you would like to discuss verbally. Just let me know.

Thank you,

Doug

[mikel]

Likely the water temp switch is the culprit, here's an option for you,

http://www.ebay.com/itm/Robertshaw-2W8915-Thermostatic-Switch-NEW-NO-BOX-/370559570475?pt=LH_Default...

This is actually an alarm switch at 98 degrees C, but at the engine temps you decribe and since your load factor is probably low this may work in a pinch.  Fast test, disconnect the temperature switch and do a test run while monitoring the gauge. I'm  not sure how your control system is wired but likely the water temp shutdown works off the Normally Open side of the switch. If it works off teh Normally Closed side then jumper the output wires.

Wish I had one laying around to give you, didn't keep a bunch of that type stuff when I left the dealership. Maybe someone in the forum has one in his truck or office he can spare.

Good luck, Mike L.

[dapaq2]

Hi Mike,

Thank you again for your reply. We are having a heck of a time trying to locate this temp switch on the engine. My understanding is that it is located somewhere in or around the thermostat housing but we have looked all over this engine and cannot find it or see anything that looks like it. Another device we are trying to locate is the Thermostatic Pilot Valve. We would like to test that device too to see if it might be the cause. But first we want to take your advice and check the temp switch, but need to find it first, but have not been able to find it yet.

Is there anyone here that has any detailed photos that show this temp switches exact location on the engine that would help us find it much quicker? Or could possibly explain in great detail as to where to look or how to find it's exact location? Also does anyone have a copy of the Cat service manual for this 3508 engine in .pdf format they would be willing to email to me? If anyone has photos, manuals, documents, schematics, or anything else on this engine that they would be willing to share with us your help would be greatly appreciated.

Thank you,

Doug

[mikel]

The water temperature switch is normally on the bottom of the thermostat housing, from the front of the engine on the right side.

The thermostatic pilot valve is only used with hydramechanical shutoff systems, typically only used on marine and petroleum service engines, never saw one on a locomotive package. So unless you know yo have the HMSO system, stop looking for the pilot valve.

Post your engine's serial number, I'll see what I can find. As for the service manual, it's a copyrighted document not usually available in PDF, however I know there have been copies come up on ebay several times lately for a very good price.

Also if this was an original engine in a military locomotive CAT Defense and Federal Products may be able to help you with some documentation.

Mike L.

[mikel]

Oops, sorry, you did post the serial number, I missed it before.

[mikel]

Well, you do have an HMSO, at least by the as shipped consist, bad for you since there are very few people left who know how they work, the parts are hard to get and/or expensive, and in general, they are a real pain in the rear.

Most customers I have worked with in the past have removed them and put on electrical safety shutdown systems. They were a great idea, put in practise they just didn't work so well, at least in my opinion. Problem is it's probably more money than you can spend.

The pilot valve should be in the same location I described for the temp switch, there will be two steel or flex lines going to it, depending on vintage. To test and see if it's the problem, temporarily remove the lines from the pilot valve and cap them, then run the unit as described before. The valve was originally sourced from AMOT, but I can't find my old info that had the AMOT part number. CAT may have one in stock, the CAT PN is 7E1121, it is part of the 2W4925 lines group.

Not sure why it got shipped that way, I'm sure someone thought it was a good idea. 

Good luck, Mike L.

[dapaq2]

Mike,

What does AMOT stand for?

Also what does it mean by 2W4925 lines group?

Thanks,

Doug

[mikel]

AMOT is the original manufacturer of the water temperature pilot valve, and they used to be available direct from them if you are looking for a lower cost option.

If you go to the dealer parts department to get a quote for the part, you can tell them the valve is part of the lines group, and they should be able to print out a picture of the parts page from SIS (the on line parts and service system) and give you a copy for reference.

Mike L.